Abstract
Lysyl oxidase (LOX) and HRAS-like suppressor (HRASLS) are silenced in human gastric cancers and are reported to have growth-suppressive activities in ras-transformed mouse/rat fibroblasts. Here, we analyzed whether or not LOX and HRASLS are tumor suppressor genes in human gastric cancers. Loss of heterozygosity and promoter methylation of LOX were detected in 33% (9 of 27) and 27% (26 of 96) of gastric cancers, respectively. Biallelic methylation and loss of heterozygosity with promoter methylation were also demonstrated in gastric cancers. Silencing of LOX was also observed in colon, lung, and ovarian cancer cell lines. As for mutations, only one possible somatic mutation was found by analysis of 96 gastric cancer samples and 58 gastric and other cancer cell lines. When LOX was introduced into a gastric cancer cell line, MKN28, in which LOX and HRASLS were silenced, it reduced the number of anchorage-dependent colonies to 57 to 61%, and the number of anchorage-independent colonies to 11 to 23%. Sizes of tumors formed in nude mice were reduced to 19 to 26%. Growth suppression in soft agar assay was also observed in another gastric cancer cell line, KATOIII. On the other hand, neither loss of heterozygosity nor a somatic mutation was detected in HRASLS, and its introduction into MKN28 did not suppress the growth in vitro or in vivo. These data showed that LOX is a tumor suppressor gene inactivated by methylation and loss of heterozygosity in gastric cancers, and possibly also in other cancers.
Highlights
Epigenetic alterations are deeply involved in cancer development and progression [1,2,3]
Noncancerous samples were obtained by scraping off noncancerous gastric mucosae for 28 cases, and by excising noncancerous gastric wall for the other 68 cases. The former samples were used for genetic analysis [mutation and loss of heterozygosity (LOH)], epigenetic analysis and expression analysis, and the latter samples were used only for genetic analysis
Entire coding regions of Lysyl oxidase (LOX) and HRAS-like suppressor (HRASLS) were analyzed by PCR-SSCP. * This nucleotide change was observed only in one ovarian cancer cell line, MCAS, for which noncancerous tissue was not available, and was considered as a somatic mutation or a rare polymorphism
Summary
Epigenetic alterations are deeply involved in cancer development and progression [1,2,3]. It is known that most important tumor suppressor genes are inactivated, by mutations and deletions and by promoter methylation. It is, expected that, if methylation-associated gene silencings are identified by genome-scanning analysis, some of the silenced genes might turn out to be tumor suppressor genes. We previously developed a genome-scanning method to search for aberrantly methylated DNA fragments, methylation-sensitive representational difference analysis In this method, unmethylated CpG-rich regions of the genome are enriched from two genomes, and the enriched libraries (amplicons) are compared by RDA [6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
